It is known to apply a ceramic insulating material over the surface of a component exposed to gas temperatures that exceed the safe operating temperature range of the component substrate material. Metallic combustion turbine (gas turbine) engine parts (e.g. nickel, cobalt, iron-based alloys) are routinely coated with a ceramic thermal barrier coating (TBC).
The firing temperatures developed in combustion turbine engines continue to be increased in order to improve the efficiency of the machines. Ceramic matrix composite (CMC) materials are now being considered for applications where the temperature may exceed the safe operating range for metal components. U.S. Pat. No. 6,197,424, assigned to the present assignee, describes a gas turbine component fabricated from CMC material and covered by a layer of a dimensionally stable, abradable, ceramic insulating material, commonly referred to as friable graded insulation (FGI). Hybrid FGI/CMC components offer great potential for use in the high temperature environment of a gas turbine engine, however, the full value of such hybrid components has not yet been realized due to their relatively recent introduction to the gas turbine industry.
Combustor liners and transition ducts are gas turbine components that have a generally tubular shape defining an interior passageway through which hot combustion gasses flow. FIG. 1 is a side view of a prior art combustor transition duct 10. Such components may be formed of an annular CMC structural member having a layer of ceramic insulating material bonded to its inside surface. Such structures are difficult to manufacture due to their complex geometry and the need for inside surface machining.